Lanthanum peridotites

LREE/HREE ratios, a difference which is also apparent from cpx compositions (Rivalenti et al., 1996). The lanthanum concentrations are typically in the range 0.005-0.05 X chondrites. Based on their REE distribution in cpx (Figure 18), the abyssal peridotites from slow-spreading ridge systems ([Pg.831]

In addition, a detailed study of a metasomatized wall rock adjacent to an amphi-bole-pyroxenite dike has revealed that the contamination in " Nd/ " " Nd and Sr/ Sr is spatially limited to a distance of <25 cm from the dike (Bodinier et al., 2003). This distance is interpreted as the chromatographic front of neodymium and strontium since the infiltration of small volume melts probably occurred on a greater distance in the host peridotite, as attested by the enrichment of the highly incompatible elements observed at 25-80 cm from the dike (e.g., lanthanum and cerium, see Section... 

Most apatites are chlorine-rich (2-4.3%) with low F/Cl (0.1 -0.3). High fluorine ( 5%) and low chlorine (—0.25%) have been reported for apatite in spinel Iherzolites from Pacific OIB (Hauri et al., 1993). Extremely high strontium contents, commonly >2X10 ppm and up to 7 wt.% (Ionov et al., 1997 Table 9) are common in mantle apatites meaning that this phase is a major repository for strontium when present in peridotites at abundances of 0.1% or above. Rb/Sr is very low. Apatites have high levels of REE and are LREE-enriched (Table 9). Lanthanum and cerium concentrations can reach >1 wt.% and neodymium concentrations can be above 1,000 ppm. Sm/Nd is below PUM. HFSE are low and so the presence of this phase does not affect bulk rock HFSE chemistry. 

---